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Bimetallic nickel-palladium

There are few reports of alkene-deuterium reactions on bimetallic catalysts, but those few contain some points of interest. On very dilute solutions of nickel in copper (as foil), the only product of the reaction with ethene was ethene-di it is not clear whether the scarcity of deuterium atoms close to the presumably isolated nickels inhibits ethane formation, so that alkyl reversal is the only option, or whether (as with nickel film, see above) the exchange occurs by dissociative adsorption of the ethene. Problems also arise in the use of bimetallic powders containing copper plus either nickel, palladium or platinum. Activation energies for the exchange of propene were similar to those for the pure metals (33-43 kJ mol ) and rates were faster than for copper, but the distribution of deuterium atoms in the propene-di clearly resembled that shown by copper. It was suggested that the active centre comprised atoms of both kinds. On Cu/ZnO, the reaction of ethene with deuterium gave only ethane-d2. as hydrogens in the hydroxylated zinc oxide surface did not participate by reverse spillover. ... [Pg.319]

Cheekatamarla and Lane ]257] found higher hydrogen yield and a lower content of light hydrocarbons for autothermal reforming of synthetic diesel fuel over bimetallic platinum/palladium and platinum/nickel catalysts compared with the monometallic samples. The catalysts showed medium-term stability for 50-h test duration in the presence of sulfur in the feed ]258]. [Pg.94]

A higher tolerance to sulfur poisoning was observed for autothermal reforming of synthetic diesel fuel over bimetallic platinum/palladium and platinum/nickel catalysts compared with monometallic samples [257]. [Pg.104]

Reetz, M.T., Breinbauer, R., and Wanninger, K., Suzuki and heck reactions catalyzed by performed palladium clusters and palladium/nickel bimetallic clusters, Tetrahedron Lett., 37, 4499, 1996. [Pg.91]

Nanosized cobalt, copper, gold, nickel, rhodium, and silver particles have been stabilized by polyions and polymers [514, 549-553]. Particularly significant has been the simultaneous reduction of HAuC14 and PdCl2 in the presence of poly(iV-vinyl-2-pyrrolidine) to give relatively uniform, 1.6-nm-diameter, palladium-coated gold bimetallic clusters [554]. [Pg.111]

The most selective and widely used catalyst is palladium, usually on an alumina support. A bimetallic palladium catalyst has also been developed.310 Palladium is more selective and less sensitive to sulfur poisoning than are nickel-based catalysts. Additionally, sulfides can also be employed. [Pg.664]

The disubstituted polypyridine derivatives, 4, 4" -bis(methylthio)-2,2 6, 2" 6", 2" 6", 2""-quinquepyridine (45) and 4, 4""-bis(methylthio)- 2,2 6, 2" 6",2" 6", 2"" 6 ", 2 ""-sexipyridine (46), in which the alkylthio groups are present on the 4-positions of the penultimate pyridines (with respect to each end) also form bimetallic double-stranded helical complexes with iron(II), cobalt(II), nickel(II), zinc(II) and palladium(II). With the first of these ligands, the palladium species is of type... [Pg.153]

Bimetallic species have also been placed into zeolites. A Pd-Ni/Y catalyst was prepared by exchange with Pd(NH3)4" 2 and Ni++. The presence of palladium enhanced the reducibility of the nickel.2 0 2l 1 Impregnation at high pH placed the nickel ions in the supercages where they were in close proximity to the reduced... [Pg.304]

Hegedus and Tamura (66) postulated that reactions of acyliron, acyl-nickel, and cobalt carbonyl anions with ij -allyl complexes of palladium proceed via unstable bimetallic intermediates with bridging o-,7r-alkenyl ligands, L (RC(0))M T7 T7--CH=CHR PdL . Products isolated from the acylation of rr-allyl ligands were a,/3- and a,y-unsaturated ketones. [Pg.229]

Bimetallic Pd/Ni [121] andPd/Co [122] systems have exhibited considerable catalytic activity in the Heck reaction of nonactivated chloroarenes with ethyl acrylate, acrylonitrile, and acrylic acid. For instance, ethyl acrylate and acrylonitrile reacted smoothly with chlorobenzene in the presence of Nal and catalytic amounts of NiBr2, Pd2(dba)3, and o-Tol3P in DMF to give E-isomers of ethyl cinnamate and cinnamonitrile, respectively [121]. The reaction occurred via the nickel-catalyzed halogen exchange between ArCl and Nal, followed by the conventional palladium-catalyzed olefination of the iodoarene generated in situ. [Pg.207]

Scientists have been interested in bimetallic systems as catalysts for many years. For a decade or longer beginning shortly after World War II, much attention was devoted to the use of metal alloys as catalysts to probe the relationship between the catalytic activity of a metal and its electronic structure (1-4). One type of alloy which was investigated extensively consisted of a Croup VIII and a Group IB metal, for instance, nickel-copper or palladium-gold. [Pg.1]

The alloy catalysts used in these early studies were low surface area materials, commonly metal powders or films. The surface areas, for example, were two orders of magnitude lower than that of platinum in a commercial reforming catalyst. Hence these alloys were not of interest as practical catalysts. The systems emphasized in these studies were combinations of metallic elements that formed continuous series of solid solutions, such as nickel-copper and palladium-gold. The use of such systems presumably made it possible to vary the electronic structure of a metal crystal in a known and convenient manner, and thereby to determine its influence on catalytic activity. Bimetallic combinations of elements exhibiting limited miscibility in the bulk were not of interest. Aspects of bimetallic catalysts other than questions related to the influence of bulk electronic structure received little attention in these studies. [Pg.2]

Several important homogeneous catalytic reactions (e.g. hydroformylations) have been accomplished in water by use of water-soluble catalysts in some instances water can act as a solvent and as a reactant for hydroformylation. In addition, formation of aluminoxanes by partial hydrolysis of alkylaluminum halides results in very high activity bimetallic Al/Ti or Al/Zr metallocene catalysts for ethene polymerization which would be otherwise inactive. Polymerization of aryl diiodides and acetylene gas has recently been achieved in water with palladium catalysts. Finally, nickel-containing enzymes, such as carbon monoxide dehydrogenase (CODH) and acetyl-CoA synthase, operate in water with reaction mechanisms comparable with those of the WGSR or of the Monsanto methanol-to-acetic-acid process. ... [Pg.799]

Beller et al. have shown for the first time that palladium colloids are effective catalysts for the olefination of aryl bromides (Heck reaction). Reetz et al. have studied Suzuki and Heck reactions catalyzed by preformed palladium clusters and palladium/nickel bimetallic clusters and further progress was achieved by Reetz and Lohmert using propylene carbonate stabilized nanostructured palladium clusters as catalysts in Heck reactions. In addition, the use of nanostructured titanium clusters in McMurry-type coupling reactions has been demonstrated by Reetz et... [Pg.921]

Monometallic systems based on Pt, Pd, Rh, Co, Cu, and also some bimetallic systems, Pt-Ag, Pt-Sn, Pd-Rh, Pt-Pb, have been developed, using a similar electrochemical deposition process [48-55]. Due to its important electrocatalytic behaviour, particles of platinum were mainly considered [48,54-66], but also bimetallic Pt-based systems, such as Pt-Ag [46], Pt-Ru [67-69] and Pt-Sn [53,68-70]. Dispersion of palladium particles was also carried out [47,71-73] and bimetallic Pd-Rh and Pd-Pt particles were also obtained [74], Deposition of nickel and copper into polypyrrole films from standard plating baths was considered recently, and observed by the Electrochemical Quartz Crystal Microbalance technique [75,76]. [Pg.477]

For industrial application usually such metals as palladium, platinum, iron, ruthenium, cobalt, molybdemun, nickel, either alone or as bimetallic catalyst are used. They are introduced using ion exchange, excess solution impregnation, incipient-wetness impregnation or physical vapor deposition methods. [Pg.217]

Other Metals. Silver, similar to gold, copper, palladium, platinum, iron, cobalt, nickel, and various bimetallics have been synthesized. As for gold, the most common sizes range in diameters of 3 to 7 nm. Ligands include the aUcyl thiols for the more noble of the metals, but these ligands are too reactive for the transition metals iron, cobalt, and nickel where long chain fatty acids can be used. [Pg.44]


See other pages where Bimetallic nickel-palladium is mentioned: [Pg.54]    [Pg.96]    [Pg.97]    [Pg.163]    [Pg.31]    [Pg.212]    [Pg.1050]    [Pg.494]    [Pg.163]    [Pg.874]    [Pg.542]    [Pg.3517]    [Pg.289]    [Pg.304]    [Pg.305]    [Pg.444]    [Pg.410]    [Pg.419]    [Pg.344]    [Pg.1261]    [Pg.116]    [Pg.3516]    [Pg.460]    [Pg.1771]    [Pg.608]    [Pg.283]    [Pg.361]    [Pg.380]    [Pg.448]    [Pg.454]   
See also in sourсe #XX -- [ Pg.67 ]




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Nickel palladium

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